Neurosurgical Focus · 2018
A Standardized System for Jugular Bulb Positions
and Microsurgical Implications in Skull Base Surgery
The Neurosurgeon
Dr. Sunil Manjila is a Michigan-based neurosurgeon whose career reflects a rare blend of rigorous training, innovative thinking, and clinical impact. His medical career began at Government Medical College, Thrissur, Keralam State of South India (Batch of 1989), inspired by a personal loss that shaped his calling to neurosurgery.
He completed his MCh (5-year program) with DNB in Neurosurgery at Christian Medical College (CMC), Vellore — one of Asia's most prestigious neurosurgical training centers — earning the Thiru Dr C V Chari Prize in Neurosciences. A short-term clinical fellowship in skull base and neurovascular surgery at Fujita Health University, Japan (2003). In 2004, he moved to the United States to pursue higher training. He subsequently undertook a full neurosurgical residency at Case Western Reserve University, Cleveland, with an enfolded fellowship.
In the US, a postdoctoral fellowship at Harvard Medical School in robotic cranial neurosurgery research led to the development of novel MR-compatible endoscopes. His pioneering work on robotics within the MRI bore has led to seminal scholastic publications. Encounters with legends Dr. Robert Spetzler and Dr. Neil Martin reinforced his commitment to systematic, reproducible neurosurgical frameworks.
The Spetzler-Martin arteriovenous malformation (AVM) grading system, proposed in 1986, assigns points for various angiographic features of intracranial arteriovenous malformations to determine a score that predicts the morbidity/mortality risk associated with open surgery (https://thejns.org/view/journals/j-neurosurg/65/4/article-p476.xml). Outside the Glasgow Coma Scale (GCS) used in neurotrauma, Spetzler-Martin grading is the most popular grading system used in cranial neurosurgery.
The Framework
A 5-tier system stratifying jugular bulb positions using high-resolution CT imaging, with sub-categories based on the presence or absence of dehiscence. Click a type to explore.
Legend — Anatomical Landmarks
| Type | Description |
|---|---|
| Type 1 | No jugular bulb |
| Type 2 | Below inferior margin of posterior SCC |
| Type 2a | Without dehiscence into the middle ear |
| Type 2b | With dehiscence into the middle ear |
| Type 3 | Between inferior margin of posterior SCC & inferior margin of IAC |
| Type 3a | Without dehiscence into the middle ear |
| Type 3b | With dehiscence into the middle ear |
| Type 4 | Above inferior margin of IAC |
| Type 4a | Without dehiscence into the IAC |
| Type 4b | With dehiscence into the IAC |
| Type 5 | Combination of dehiscences |
The Publication
This paper addressed a long-standing ambiguity in skull base surgery: the absence of a universally accepted definition for high-riding jugular bulb (HRJB). Different specialties — radiology, neurotology, and neurosurgery — used variable criteria, leading to miscommunication and surgical risk. The Manjila-Semaan system used high-resolution CT imaging to stratify jugular bulb positions into five major types with sub-categories based on dehiscence, directly aligning radiological anatomy with operative decision-making and enabling clear, reproducible interdisciplinary communication.
Presentation
A complete walkthrough of the Manjila-Semaan Classification System — its rationale, anatomical basis, and surgical implications.
Clinical Validation
Since its publication, the Manjila-Semaan Classification has been validated across multiple independent clinical and academic studies all over the world.
Journal of Neurological Surgery Part B: Skull Base
Demonstrated high inter- and intrarater reliability of the classification system across varying levels of radiological experience — a critical milestone for widespread clinical adoption in surgical planning.
Read Study →Neurosurgical Review · Springer
Applied the classification to preoperative CT evaluations in patients undergoing vestibular schwannoma excision, confirming that Type 4 jugular bulbs significantly increase the risk of venous injury during drilling — enabling proactive surgical planning.
Read Study →The Journal of Laryngology & Otology · 2025;139(10) · Das NK, Keshri A, Manogaran RS, et al.
A neuro-otology team at SGPGIMS, Lucknow independently validated the classification for otologic and lateral skull base surgery, confirming its reliability in preoperative surgical planning.
Read Study →J Coll Physicians Surg Pak (JCPSP) · 2026;36(1):20–24 · Uddin MMZ, Jamil A, Hashmi SQ, et al.
Applied the classification to HRCT temporal bone imaging in a Pakistani population, characterising jugular bulb type variability across age groups.
Read Study →Medicina (Kaunas) · 2024;60(9):1408 · MDPI
Peer-reviewed imaging study referencing the Manjila-Semaan framework in the radiological assessment of jugular bulb anatomy.
Read Study →J Case Reports & Medical History · 2024 · Alnafie MA, Moualek S, Ghebriout B
A rare case report applying the classification to a previously undocumented pattern of bilateral high-riding jugular bulb with mastoid and Trautmann's triangle dehiscence.
Read Study (PDF) →Aging and Disease · 2020;11(4):770–776
A population-based study assessing the prevalence of high-riding jugular bulb across adult age groups, referencing standardised classification landmarks.
Read Study →ECR 2025 · European Congress of Radiology · Poster C-14849 (Cum Laude) · Alec A, Balica NC, Ungureanu AM
An educational radiology poster citing the classification among key temporal-bone findings that inform cochlear implant surgical planning.
View References →Anatomical Science International · Springer · 2026 · doi:10.1007/s12565-026-00919-9
An anatomical study referencing the Manjila-Semaan classification in the morphometric analysis of jugular bulb variants.
Read Study →Frontiers in Pediatrics · 2023 · Liu J, Xie W, Ding Y, et al.
Correlated audiological findings with high-riding jugular bulb anatomy, referencing the classification for anatomical stratification.
Read Study →Surgical & Radiologic Anatomy · 2023 · Juelke E, Butzer T, Anschuetz L, et al.
Used 3D reconstructions of 46 temporal bones to quantify jugular bulb variability, correlating measurements with classification types for surgical guidance.
Read Study →ResearchGate · Prospective Study · 2025
A prospective study proposing standardised radiological reporting of jugular bulb variants using lateral skull base landmarks, building on the Manjila-Semaan system.
Read Study →Frontiers in Neurology · 2023 · Xia K, Lei P, Liu B, et al.
Compared jugular bulb and vestibular aqueduct abnormalities in 103 Ménière's disease patients versus controls, using standardised jugular bulb classification for assessment.
Read Study →Engineering & Patents
Beyond classification, Dr. Manjila's work extends into hardware innovation — designing instruments that redefine what is possible inside the operating theatre and the MRI bore.
Conventional rigid endoscopes limit the surgeon to a single axis of vision at the instrument tip, requiring repeated rotation and risking tissue compression. Flexible scopes improve steerability but sacrifice channel capacity and control. Dr. Manjila's innovation bridges both — a hybrid rigid endoscope with two independent optical ports (tip and lateral), each with its own CMOS camera and LED illumination, plus a compliant silicone tip window that enables pre-deployment instrument visualisation and imaging in blood-filled fields.
Validated in porcine brain models, human cadaver studies, and inside a 3-Tesla MRI scanner, the prototype performed combined ventricular procedures with less than 5° of endoscope rotation. Its customisable port configurations, reduced brain distortion risk, and full MR compatibility open new frontiers — from laser-assisted tumour treatment to management of complex postinflammatory hydrocephalus — and form the basis of a granted US patent.
Principal Investigator: Pierre E. Dupont, PhD
https://robotics.tch.harvard.edu/
Academic Works
Beyond the jugular bulb classification, Dr. Manjila's scholarship encompasses endoscopic cranial neurosurgery, skull base pathology, and the novel field of robotic cranial neurosurgery.
World Neurosurgery · 2023 Aug;176:127-139
A comprehensive review of robotic cranial neurosurgery paradigms operating within MRI bore environments, examining imaging guidance, safety, and future directions.
DOI: 10.1016/j.wneu.2023.01.025 →Neurosurgical Focus · 2016 Sep;41(3):E13
Introduced a novel multiport neuroendoscope design compatible with MRI environments, bridging the functional gap between rigid and flexible endoscopic systems — basis of a US patent.
DOI: 10.3171/2016.7.FOCUS16181 →Operative Neurosurgery · 2019 Feb;16(2):217-225
Demonstrated a minimally invasive surgical technique for bilateral anterior cingulotomy using a novel multiport cisternoscope, offering a cadaveric proof-of-concept for pain surgery approaches.
DOI: 10.1093/ons/opy083 →Details to be announced
A new paper by Dr. Sunil Manjila is currently in preparation. Details will be updated upon publication.
Get in Touch
For academic inquiries, copyright or collaboration requests, or clinical correspondence regarding the Manjila-Semaan Classification.